Firefighters look over the site of a building explosion in New York, Friday, March 14, 2014. Using sound devices to probe for voices and telescopic cameras to peer into small spaces, workers searching a pile of rubble from a gas explosion in the East Harlem section of Manhattan, continued to treat it as a rescue operation, holding onto the possibility of finding survivors from a blast that brought down two apartment buildings and killed at least eight people. (AP Photo/Seth Wenig)

People hold up candles while praying during a vigil for the victims of an explosion, Thursday, March 13, 2014 in New York. Rescuers working amid gusty winds, cold temperatures and billowing smoke pulled four additional bodies from the rubble of two New York City apartment buildings, raising the death toll to at least seven from a gas leak-triggered explosion that reduced the area to a pile of smashed bricks, splinters and mangled metal. The explosion Wednesday morning in Manhattan's East Harlem injured more than 60 people. (AP Photo/Julio Cortez)

An excavator removes debris from the site of a building explosion, Thursday, March 13, 2014 in New York. Rescuers working amid gusty winds, cold temperatures and billowing smoke pulled four additional bodies Thursday from the rubble of two New York City apartment buildings, raising the death toll to at least seven from a gas leak-triggered explosion that reduced the area to a pile of smashed bricks, splinters and mangled metal. The explosion Wednesday morning in Manhattan's East Harlem injured more than 60 people. (AP Photo/Mark Lennihan)

NEW YORK (AP) — All eight people reported missing after a deadly New York City gas explosion have been recovered, the fire commissioner said Friday, but workers are still treating the scene as a rescue operation in case there are unknown survivors in the rubble.

Salvatore Cassano said no one else is known to be unaccounted for, but workers will continue to scour the debris from two flattened apartment buildings for victims. More than 60 people were injured and more than 100 others displaced by the Wednesday morning explosion.

Cassano said 60 to 70 percent of the debris had been cleared at the East Harlem blast site. But he said the pace was expected to quicken after firefighters removed a hazardous rear wall.

He predicted detectives and fire marshals would gain access to the buildings' basements by mid-day Saturday to begin the investigation into what caused the explosion.

"Right now we are in the process of removing the final amount of debris," Cassano said at a news conference outside the Red Cross shelter where families have been placed temporarily. "We should be moving much more quickly now."

Police have identified six of the dead: Griselde Camacho, 45, a Hunter College security officer; Carmen Tanco, 67, a dental hygienist who took part in church-sponsored medical missions to Africa and the Caribbean; Andreas Panagopoulos, 43, a musician; Rosaura Hernandez, 22, a restaurant cook from Mexico; George Ameado, 44, a handyman who lived in one of the buildings that collapsed; and Alexis Salas, 22, a restaurant worker.

Mexican officials said a 43-year-old Mexican woman, Rosaura Barrios Vazquez, was among those killed.

The eighth body, a woman, was pulled from the rubble on Thursday. Her name hasn't been released.

Mayor Bill de Blasio, who toured the shelter with other city officials, said Friday that the city would find temporary or long-term housing for about 50 displaced families, totaling more than 100 people.

The Department of Homeless Services has about 50 apartments available for families in private buildings where nonprofits are involved in the management, he said, adding that officials are arranging for more apartments that would be available for up to three months.

"It's our obligation as the city of New York, and I know all New Yorkers feel this way, to stand by them," he said of the residents.

Investigators were trying to pinpoint the gas leak and determine whether it had anything to do with the city's aging gas and water mains, some of which were installed in the 1800s. The National Transportation Safety Board, which investigates pipeline accidents, will conduct an inquiry after police and fire officials locate what might have sparked the blast.

Cassano said Friday they'll look at meters, see if there were any breaks in the piping and identify any possible ignition sources, such as light switches.

NTSB team member Robert Sumwalt said Thursday the gas main and distribution pipe under the street had been examined in a crater and were found to be intact, with no obvious punctures or ruptures. They had not been torn from the ground.

However, he said NTSB investigators had been unable to conduct a fuller examination because of the rescue effort, and it was unclear whether the leak came from inside or outside the buildings.

Sumwalt said there had also been a water main break at the site, but it was unknown if that contributed to the gas explosion or was caused by it. The water main was installed in 1897, according to the city.

Fire and utility officials said that if the buildings were plagued in recent days or weeks by strong gas odors, as some tenants contended, they have no evidence anyone reported it before Wednesday.

The blast erupted about 15 minutes after someone from a neighboring building reported smelling gas, authorities said. The Con Edison utility said it immediately sent workers to check out the report, but they got there too late.

Con Ed CEO John McAvoy said the call had been correctly categorized as low priority. "A single person calling that they smelled gas outside of a building is not something that would warrant a fire department response," he said.

NYPD spokesman Stephen Davis said detectives have interviewed the landlords of both buildings to help identify occupants and tenants but said none of them reported being told about gas leaks or odors.

An Associated Press analysis of the city's 311 calls database from Jan. 1, 2013, through Tuesday also found no calls from the buildings about gas.

The lesson, De Blasio said, is that people should heed the post-Sept. 11, 2001, slogan, "If you see something, say something."

More than 30,000 miles of decades-old, decaying cast-iron pipe are still being used to deliver gas nationwide, according to the U.S. Transportation Department estimates. In 2011, the American Gas Association said replacement or repair could cost $82 billion.

New York City still uses about 3,000 miles of old cast iron, Boston about 2,000 miles, Philadelphia about 1,500 and Washington 400, the department said. Experts said much of the pipe dates to before World War II, and some of it is more than 100 years old.

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